1. Field of the Invention
The present invention relates to improvements in comminuting machines for coal, rocks, stones and the like, and more particularly to improvements in comminuting machines, such as impact wherein the width of the clearance between at least one first and at least one second comminuting or crushing tool is variable to permit selection of the size of comminuted material and/or to compensate for wear upon the parts of the comminuting tools. The invention also relates to a method of operating a comminuting machine of the above outlined character.
2. Brief Description of the Background of the Invention Including Prior Art
A comminuting machine normally comprises at least one first comminuting tool, e.g., a rotor with one or more material crushing or comminuting components called beaters and constituting or including plates, vanes or like parts, a drive which moves the beaters of the first tool along a predetermined path, e.g., along an endless path, at least one second tool, e.g., in the form of a pivotable or otherwise movable impact plate, and means for moving the second tool relative to the first tool in order to vary the width of the clearance between the two paths, i.e., to select the maximum size of comminuted particles of material which is being admitted into the inlet or inlets of the housing for the first and second tools. It is customary to adjust the position of the second tool relative to the first tool at certain intervals in order to compensate for wear upon the beaters and/or upon the impact plate, i.e., in order to compensate for an undesirable increase of the width of the clearance.
In accordance with a prior proposal, the means for moving the second tool relative to the first tool are actuated to move the impact plate toward the path of movement of the beaters whereby the beaters strike the impact plate with attendant generation of sound or noise having a certain intensity. Such noise or sound is monitored by a microphone which generates signals denoting the development of sound as a result of impingement of beaters upon the second tool. These signals enable an operator to reverse the direction of movement of the second tool, namely in a direction away from the first tool, until the width of the clearance reaches a desired value. Such procedure of correcting the width of the clearance at certain intervals can be resorted to in connection with impact crushers, and analogous comminuting machines. Intermittent adjustments of the width of the clearance are necessary because the wear upon the components of the first and second tools is, or can be, pronounced whereas the users of comminuting machines strive to produce comminuted rocks, coal or other materials having a predetermined maximum particle size. As a rule, or at least in many instances, the comminuting component or components of the second tool are pivotable toward and away from the path of movement of beaters forming part of the first tool. This holds true irrespective of whether the machine is an impact crusher with or without a grinding track which is located downstream of the clearance between the first and second tools.
The procedure to alter the width of the clearance between the first and second tools in a conventional comminuting machine is a time-consuming chore which invariably involves substantial losses in output. Thus, it is normally necessary to arrest the machine and to open the housing for the tools in order to afford access to the clearance which is then measured in order to ascertain whether or not the wear upon the components of the tools is sufficient to warrant an adjustment of the clearance. As mentioned above, the wear upon the components of the tools which define the clearance is often quite pronounced so that the machine must be arrested at rather frequent intervals.
The published German Patent Application No. 2,018,496 proposes to avoid stoppage of the comminuting machine for the sole purpose of altering the width of the clearance between the first and second tools. This is to be achieved by employing a contact-free proximity detector which is intended to prevent movements of the second tool into actual contact with the beaters of the first tool. It has been found that such proposal is unsatisfactory and, therefore, the machine which is disclosed in the published patent application No. 2,018,496 failed to gain acceptance in the industry.
Another proposal to avoid stoppage of the comminuting machine for the express purpose of altering the width of the clearance is disclosed in published German patent application No. 2,034,672. This publication suggests to carry out a number of experiments with different types of materials which are to be comminuted and to ascertain the anticipated wear upon the components of the first and second tools when the machine is in use to comminute a particular material. The results of such experiments are to be utilized for intermittent adjustment of the second tool by moving it toward the first tool in order to compensate for anticipated wear. The adjustment of the width of the clearance can be carried out continuously or in stepwise fashion. The operation of such machines is unreliable because it is difficult to ascertain, in advance, the exact composition, including the hardness and the size, of a material which is to be comminuted. Moreover, proper reliance on the just discussed procedure necessitates the carrying out of extensive experiments and the utilization of rather complex controls for the mechanism which serves to move the second tool relative to the first tool.
In accordance with the aforediscussed first prior proposal, the admission of material into the housing of the comminuting machine is interrupted and the second tool is slowly moved toward the first tool until it is actually struck by the beaters of the first tool. This results in the generation of pronounced noise which is ascertained with a microphone. The movement of the second tool toward the first tool is then interrupted and the direction of movement of the second tool is reversed until the width of the clearance is increased to a desired value. A machine of the just described character is described and shown in the German-language publication entitled "Aufbereitungstechnik". Reference may be had to FIG. 7 and to the article entitled "Hartzerkleinerungsmaschinen fur neue Verfahrenstechniken" (1975, Volume 8). The same machine is described in the servicing manual which was first published Dec. 12, 1974 and refers to an impact crusher which was distributed by HAZEMAG Dr. E. Andreas GmbH & Co., Munster, Federal Republic Germany. All necessary manipulations including starting the means for moving the second tool in a direction toward the first tool, reversing the direction of movement of the second tool when the microphone furnishes signals denoting that the beaters of the first tool strike the second tool, and arresting the moving means for the second tool are carried out by hand. A somewhat similar machine is disclosed in U.S. Pat. No. 3,035,782.
A drawback of the HAZEMAG machine and of the machine which is described in U.S. Pat. No. 3,035,782 is that the operator must be on the alert to immediately reverse the direction of movement of the second tool when the microphone generates a signal denoting that the second tool is being struck by the beaters of the first tool. This requires much concentration on the part of the attendant, and the operator must be able to react quickly in order to avoid prolonged interruptions of operation and potential extensive damage to the parts of the comminuting machine.